Variable choke assembly

ABSTRACT

A pressure reducing apparatus for controlling the pressure of oil is provided. The apparatus has ceramic components that resist wear caused by sand and debris in the oil. In one embodiment of the invention, the apparatus has a hollow body having an upstream channel, a downstream channel, and a pressure reducing chamber between the upstream channel and the downstream channel. The pressure reducing chamber has a longitudinal axis and contains a disk that is rotatable on the longitudinal axis of the pressure reducing chamber. The disk has a sidewall that abuts the upstream channel and a bottom end that abuts the downstream channel. The sidewall has a height that varies along the circumference of the disk. The disk is rotatable within the pressure reducing chamber so that the height of the sidewall facing the upstream channel can be varied to throttle the flow of oil from the upstream channel.

RELATED APPLICATIONS

[0001] This application claims priority under 35 U.S.C. §120 from U.S.application Ser. No. 10/130,651, filed as International Application No.PCT/US00/32150 on Nov. 28, 2000, which is hereby incorporated herein byreference.

FIELD OF THE INVENTION

[0002] This invention relates generally to flow components for highpressure oil wells, and in particular to the use of ceramic material inwear components for a pressure reducer assembly for such wells.

BACKGROUND

[0003] Many oil well facilities around the world operate under highpressure. In other words, the pressure within the well is sufficientlyhigh (e.g., 3000 to 5000 psi) to carry the crude oil to the surfacewithout pumping. Unless restricted, the crude oil flows to the surfaceat a high velocity and contains sand and other debris which erodes theinterior surfaces of the oil well piping components. In order to limitthe amount of sand and debris that is carried with the extracted oil,the high well pressure is maintained in the exit piping by using apressure reducer at the head end of the well. For instance, a six inchinner diameter well pipe is reduced to three inches through a series ofnarrow channel pipe components. The flow channel is then further reducedto less than one inch, or even less than one-half inch, in the pressurereducer assembly.

[0004] The known pressure reducing devices are made of carbon steel andhave tungsten carbide inserts to line the inside surfaces of the flowchannels. The abrasive oil-and-sand mixture not only wears away theinside wall of the flow channels, but also backwashes around the outsidediameter of the flow reducer and wears away the steel body of the flowreducer, resulting in gross failure of the reducer itself. Often, themetal housing surrounding the flow reducer is severely worn as well.Continuous erosion of the pressure reducer over time results in a slowand continuous loss of desired operating pressure until gross failurerequires replacement. This loss in operating pressure causes anever-increasing sand content, resulting in less efficient oilproduction. Eventually, the oil line must be shut off, and the entirepressure reducer device must be disconnected from the line and replaced.

[0005] The average life of known flow reducers is about 4 to 12 weeks.Oil well downtime to replace a pressure reducer and/or other components,is usually four to eight hours. Since high pressure oil wells typicallyproduce about 5,000 to 12,000 barrels of oil a day, the downtimeassociated with replacement of a pressure reducer can result in asignificant loss of oil production. It is readily apparent that thepresent construction of oil well pressure reducing assemblies leavessomething to be desired with respect to wear resistance, useful life andserviceability.

SUMMARY OF THE INVENTION

[0006] In a first aspect of the present invention, a pressure reducingapparatus is provided that has an extended operating life. The internalcomponents of the apparatus are made entirely of wear resistantmaterials that minimize abrasion caused by sand and other debris in oil.In one embodiment of the invention, the apparatus has a housing thatforms an upstream channel and a downstream channel. The housing has aport that fluidly connects the housing with the upstream channel. A diskdisposed in the housing is rotatable between a first orientation inwhich the port is substantially obstructed by the disk and a secondorientation in which the port is substantially unobstructed by the disk.The disk has a side wall that covers the port when the disk is rotatedto the first orientation to substantially prevent fluid in the upstreamchannel from entering the housing. As such, the disk is rotatable tothrottle the flow of oil and alter the pressure in the pressure reducingassembly.

DESCRIPTION OF THE DRAWINGS

[0007] The foregoing summary as well as the following description willbe better understood when read in conjunction with the figures in which:

[0008]FIG. 1 is a side elevation view of a pressure reducing assemblyfor a high pressure oil well;

[0009]FIG. 2 is a side elevation view in partial cross section showingthe interior of the pressure reducing assembly of FIG. 1 as viewed alongline 2-2 thereof;

[0010]FIG. 3 is a cross-sectional side view of a ceramic liner used inthe upstream channel of the pressure reducing assembly of FIG. 2, asviewed along line 3-3 thereof;

[0011]FIG. 4 is a cross-sectional side view of an alternative embodimentof the ceramic liner shown in FIG. 3;

[0012]FIG. 5A is side view of a direction changing cavity liner used inthe pressure reducing assembly shown in FIG. 2;

[0013]FIG. 5B is an end view of the direction changing cavity linershown in FIG. 5A as viewed along line 5B-5B thereof;

[0014]FIG. 6A is a side view of a key plate liner used in the pressurereducing assembly shown in FIG. 2;

[0015]FIG. 6B is an end view of the key plate liner shown in FIG. 6A asviewed along line 6B-6B thereof;

[0016]FIG. 7 is a cross-sectional side view of a downstream cylindricalliner used in the pressure reducing assembly of FIG. 2, as viewed alongline 7-7 thereof;

[0017]FIG. 8 is a side view of a ceramic flow reducer used in thepressure reducing assembly shown in FIG. 2;

[0018]FIG. 9 is a side view of an alternative embodiment of the ceramicflow reducer shown in FIG. 8;

[0019]FIG. 10 is a side elevational view in cross section showing aspool adapter assembly used in the pressure reducing assembly of FIG. 1as viewed along line 10-10 thereof;

[0020]FIG. 11 is a side elevation view of a second embodiment of apressure reducing assembly according to the present invention;

[0021]FIG. 12 is a cross-sectional side view of a ceramic liner used inthe upstream channel of the pressure reducing assembly of FIG. 11, asviewed along line 12-12 thereof; and

[0022]FIG. 13 is a cross-sectional view of a downstream liner used inthe pressure reducing assembly of FIG. 11, as viewed along line 13-13thereof.

[0023]FIG. 14 is a side perspective view in partial cross sectionshowing the interior of a third embodiment of the pressure reducingassembly of FIG. 1 as viewed along line 2-2 thereof;

[0024]FIG. 15 is an exploded perspective view of the pressure reducingassembly of FIG. 14.

[0025]FIG. 16 is a detailed exploded perspective view of the valveassembly used in the pressure reducing assembly of FIG. 14.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0026] Referring now to the drawings wherein like reference numeralsindicate identical or corresponding parts among the several views and inparticular to FIG. 1, there is shown a pressure reducing assembly for ahigh-pressure well head. For purposes of orientation, the oil floworiginating from the well flows through the pressure reducing assemblyaccording to the present invention and toward the oil process piping inthe direction shown by the arrows. A pressure reducing valve 10 isconnected through an isolation valve 19 to a well head manifold 25. Thedownstream side of pressure reducing valve 10 is connected to a firstspool adapter 20, which is connected to a second spool adapter 30. Thesecond spool adapter 30 is connected to the piping that leads to the oilprocessing facilities (not shown).

[0027] Referring now to FIG. 2, the pressure reducing valve 10 has ametallic body that includes an upstream channel 11, a direction-changingcavity 16, a downstream channel 17, and a key-plate recess 18. Apressure reducer 40 is disposed in the downstream channel 17 and has ahex head 42 and a sealing shoulder 43 that extend into thedirection-changing cavity 16, adjacent the upstream channel 11. Anupstream channel liner 50 is disposed in the upstream channel 11 and adownstream channel liner 80 is disposed in the downstream channel 17.The channel liners 50 and 80 prevent erosion of the inner walls of thechannels 11 and 17, respectively, by the oil/sand mixture flowing fromthe oil well. A direction-changing cavity liner 60 is situated in thedirection-changing cavity 16 to prevent erosion and wear of the innerwall of the direction changing cavity 16. A key plate liner 70 isdisposed in a key-plate recess 18 situated at an end of thedirection-changing cavity 16 adjacent the downstream channel 17. The keyplate liner 70 prevents erosion and wear of the metal wall of thekey-plate recess 18.

[0028] An end cap 15 is provided to close off the direction changingcavity 16. The end cap 15 is removable to permit access to the directionchanging cavity 16 for installing and removing the direction changingcavity liner 60 and the key plate liner 70. The end cap 15 can beunthreaded and removed to provide access to direction changing cavity16. The direction changing cavity liner 60 is removed by sliding it outof the direction changing cavity 16. Once the direction changing cavityliner 60 is removed, the key plate liner 70 can be removed by tilting itout of key plate recess 18 and pulling it through the directionalchanging cavity 16 and out of the access opening. When the directionchanging cavity liner 60 and the key plate liner 70 are removed, the hexhead 42 of the pressure reducer 40 is accessible for removal orinstallation of the pressure reducer 40.

[0029] End cap 15 has a port 13 formed therethrough to provide aconnection point for a pressure gauge or other pressure sensing device.A second port 14 is formed in the body of pressure reducing valve 10adjacent to the key-plate recess 18 to provide a connection point for asecond pressure gauge or sensing device.

[0030] The upstream channel 11 is generally cylindrical and has an inletportion characterized by a first diameter and an outlet portion 52 thatis characterized by a second diameter smaller than the first diameter.The inlet portion and the outlet portion meet at an upstream channelmaintenance point 12 which serves as a stop for the upstream channelliner 50. Referring now to FIG. 3, there is shown an upstream channelliner 50 in accordance with the present invention. The upstream channelliner 50 is generally cylindrical and has an inlet portion and an outletportion. The inlet portion has a diameter that is generally commensuratewith the inside diameter of the inlet portion of upstream channel 11 andthe outlet portion has an outside diameter that is generallycommensurate with the inside diameter of the outlet portion of upstreamchannel 11. That arrangement provides a shoulder stop 53 on the exteriorof the upstream channel liner 50 which abuts the upstream channelmaintenance point 12 when inner end 52 is inserted into the upstreamchannel 11. The abutment of the shoulder stop 53 with the maintenancepoint 12 prevents the liner from shifting toward the direction changingcavity 16 when oil is flowing. The upstream channel liner 50 has aninternal channel that extends from an opening 51 to the outlet portion52. The opening is preferably flared to lessen flow turbulence as theoil enters the upstream channel liner 50. In the embodiment shown inFIG. 3, the internal channel tapers to a smaller cross section as ittraverses the outlet portion 52. The tapered channel portion 54 relievessome of the pressure and turbulent flow of the oil as it flows throughthe upstream channel 11. The upstream channel liner 50 is formed of aceramic material.

[0031] Shown in FIG. 4 is an alternative embodiment of the upstreamchannel liner 50. In the embodiment shown in FIG. 4, the internalchannel 55 has a uniform cross section to maximize flow.

[0032] Referring now to FIGS. 2, 5A, and 5B, the direction changingcavity liner 60 is disposed within the directional changing cavity 16 ofpressure reducing valve 10. The directional changing cavity liner 60 isformed of a ceramic material. The liner 60 is generally cylindrical andhas an outside diameter that is dimensioned to provide a snug fitbetween the outer surface of the liner 60 and the inner surface of thecavity 16. A recess 64 is formed in one end of the liner 60. The recessis dimensioned to provide a space around the head 42 and shoulder 43 ofthe pressure reducer 40 when it is fully threaded into the downstreamchannel 17. A central through-hole 61 extends along the length of thedirection changing cavity liner 60 to provide a path between the recess64 and the port 13 for pressure indication. The directional changingcavity liner 60 has a key-way 62 formed thereon which extendslongitudinally partially along the exterior of direction changing cavityliner 60. The directional changing cavity liner 60 also has a key platethru-hole 63 formed therein between the recess 64 and the key-way 62 toprovide fluid communication between recess 64 and port 14.

[0033] Referring now to FIGS. 2, 6A, and 6B, the key plate liner 70 ispositioned within the key plate recess 18 of reducing valve 10. Keyplate liner 70 contains a key plate thru-hole 71 which aligns with thekey plate port 14 and the key plate thru-hole 63 to provide fluidcommunication between the recess 64 and the key plate port 14. Key plateliner 70 also has a key 72 formed thereon which is dimensioned to matewith the key-way 62 in liner 60 to ensure proper alignment of the keyplate liner 70 and the cavity liner 60. The key plate liner 70 is formedof a ceramic material.

[0034] Referring now to FIGS. 2 and 7, the downstream channel liner 80is disposed within the downstream channel 17. The downstream channel 80is generally cylindrical in shape and has an outside diameter that isdimensioned to provide a tight fit with the downstream channel 17.Because of that arrangement, the downstream liner 80 prevents the oilfrom backwashing between the liner and the interior wall of downstreamchannel 17. The downstream channel 80 extends less than the full lengthof the downstream channel 17 so that an attachment region is providedwhere the pressure reducer 40 can be attached to the body of thepressure reducing valve 10. In the embodiment shown, the pressurereducer 40 is attached by threading it into the downstream channel 17.The downstream channel liner 80 is formed of a ceramic material.

[0035] As shown in FIG. 2, pressure reducer 40 is situated in downstreamchannel 17 and projects into direction changing cavity 16. Referring nowto FIG. 8, there is shown a preferred arrangement for the pressurereducer 40. The pressure reducer 40 is generally cylindrical and has anoutside diameter that is substantially commensurate with the insidediameter of downstream liner 80. A series of screw threads 44 are formedon the outer surface adjacent the shoulder 43. The pressure reducer 40is formed of a ceramic material. A central channel 45 extendslongitudinally through the body of the pressure reducer 40 from entryport 41 to an outlet port 49. The central channel 45 flares to a largerinside diameter to provide a pressure reducing effect as the oil flowsfrom entry port 41 through the central channel. When the pressurereducer 40 is threaded into the downstream channel 17, sealing shoulder43 presses against a washer or gasket to provide a fluid-tight sealagainst the abrasive flow of oil and sand from direction changing cavity16. The washer or gasket is preferably formed of Buena-N gasket materialor an equivalent thereof.

[0036]FIG. 9 shows a second alternative embodiment of pressure reducer40. The embodiment shown in FIG. 9 has a generally cylindrical bodyincluding a head portion 92 with a plurality of entry holes 46 formedtherein to provide an inlet for the oil. The pressure reducer 40 has acentral channel 48 formed longitudinally therethrough. The centralchannel 48 has a substantially uniform cross section along its lengthand extends from the head portion 92 to an outlet port 94 in the otherend of the pressure reducer 40. The entry holes 46 are in fluidcommunication with the central channel 48. A hexagonal shoulder 47 isformed about the circumference of the pressure reducer 40 adjacent thehead portion 92. The hexagonal shoulder 47 performs the functions of thehex head 42 and shoulder 43 of the embodiment shown in FIG. 8.

[0037] Referring back to FIG. 2, upstream cylindrical liner 50 anddownstream cylindrical liner 80 are removed by un-bolting flangeconnections at both ends of reducing valve 10, removing reducing valve10 from the process piping, and sliding upstream cylindrical liner 50and downstream cylindrical liner 80 out of upstream canal 11 anddownstream canal 17, respectively. The liners are installed by reversingthis process.

[0038] Referring now to FIG. 10, there is shown a spool assemblyincluding a first spool adapter 20 and second spool adapter 30. Firstspool adapter 20 has a steel body with a central longitudinal channel 21having a substantially uniform cross section along the length thereof. Aceramic channel liner 22 having a substantially uniform outside diameter23 that is dimensioned to provide a light press fit in the centralchannel 21 of first spool adapter 20. The ceramic channel liner 22extends substantially the entire length of the central channel 21.Channel liner 22 has a flow channel 24 that extends the length of thechannel liner 22. The cross section of the flow channel 24 graduallywidens in the direction of the oil flow from the inlet of the spooladapter 20 adjacent the pressure reducing valve 10 to its outletadjacent the second spool adapter 30. The gradual widening or flaring ofthe flow channel 24 minimizes turbulent, abrasive, flow that wouldaggravate the wear and erosion caused by the flow of oil and sandtherethrough, thus increasing the useful life of the spool adapter 20.

[0039] The second spool adapter 30 has a steel body with a centrallongitudinal channel 31. A ceramic channel liner 32 has a substantiallyuniform outside diameter 33 that is dimensioned to provide a light pressfit in the central channel 31 of second spool adapter 30. Ceramicchannel liner 32 has a flow channel 36 that extends from the inletadjacent the first spool adapter to the outlet adjacent the downstreamprocess piping (not shown). The central channel 36 has a flared portion34 and a uniform cross section portion 35. The flared portion 34 extendsfrom the inlet along part of the length of ceramic liner 32. The degreeof flaring is such as to continue the flaring of the flow channel 24 ofthe first spool adapter 20. The inside diameter of the uniform crosssection portion 35 is dimensioned to be commensurate with the insidediameter of the downstream process piping.

[0040] As described above, the pressure reducer 40, upstream channelliner 50, direction changing cavity liner 60, key plate liner 70,downstream channel liner 80, and the central longitudinal channel liners22 and 32, are all formed of a ceramic material. The ceramic material isselected from the class of technical ceramics, particularly technicalceramic materials that exhibit superior wear resistance and strength.Among the preferred ceramic materials are aluminum oxide (alumina),chromium oxide, high alumina, titanium oxide (titania), zirconium oxide(zirconia) ceramics, including fully and partially stabilized zirconia,and combinations of such metal oxides. It is believed that just aboutany type of metal-oxide ceramic will provide acceptable properties.Excellent results have been achieved using partially stabilized zirconia(PSZ) for making the aforesaid components. Particular species of PSZthat are believed to be useful for the aforesaid components includeMg-PSZ and vitreous PSZ. Silicon nitride, quartz, and silicon carbideceramics are also expected to be useful in such components.

[0041] Referring now to FIG. 11, there is shown an alternativeembodiment of a pressure reducing valve according to the presentinvention. The pressure reducing valve 110 has a metallic body 120 thatincludes an upstream channel 111 and a downstream channel 117. Upstreamchannel 111 has an inlet portion 115 and an outlet portion 116 whichmeet at a maintenance point 112. An upstream channel liner 150 isdisposed in the upstream channel 111, and likewise, a downstream channelliner 180 is disposed in the downstream channel 117. Channel liners 150and 180, among other things, prevent erosion of the inner walls of thechannels 111 and 117, respectively, by the oil/sand mixture flowingthrough pressure reducing valve 110, from the oil well. A gauge port 114is formed in the metallic body 120 to provide a connection point for apressure gauge, or other sensing device. Gauge port 114 has one end incommunication with downstream channel 117.

[0042] Upstream channel liner 150 is slidably disposed within upstreamchannel 111. As shown in FIG. 12, the upstream channel liner 150 isgenerally cylindrical and has an inlet portion 151, which ischaracterized by a first diameter, and an outlet portion 152, which ischaracterized by a second diameter smaller than the first diameter.Inlet portion 151 has an outside diameter that is generally commensuratewith the inside diameter of the inlet portion 115 of upstream channel111 and the outlet portion 152 has an outside diameter that isessentially commensurate with the inside diameter of the outlet portion116 of upstream channel 111. That arrangement provides a shoulder 153which abuts the maintenance point 112 when channel liner 150 is insertedinto upstream channel 111. The abutment of shoulder 153 with maintenancepoint 112 prevents the liner 150 from shifting toward downstream liner180 when oil is flowing through reducing valve 110. The upstream channelliner 150 has an internal channel 154 that extends from the inletportion 151 to the outlet portion 152. Channel 154 is preferably taperedto lessen flow turbulence as oil flows through upstream channel liner150. In the embodiment shown in FIG. 12, the internal channel tapers toa smaller cross section as it traverses to the outlet portion 152. Theupstream channel liner 150 is preferably formed of a ceramic material asdescribed above.

[0043] Downstream channel liner 180 is slidably disposed in thedownstream channel 117, as shown in FIG. 11. Referring now to FIG. 13,downstream channel liner 180 is generally cylindrical and has an inletend 181 and an outlet end 182. Downstream channel liner 180 has athrough-hole 183, which is oriented and positioned to align with gaugeport 114. Through-hole 183 extends radially through channel liner 180and is in fluid communication with internal channel 184 of the channelliner 180. A recess 185 is formed in liner 180; at the inlet end 181.Recess 185 is generally cylindrical in shape and is dimensioned andpositioned to receive the inner end 155 of upstream liner 150. Channel184 extends between the inlet end 181 and the outlet end 182 of liner180. Channel 184 is flared near outlet end 182 to minimize turbulentflow that would aggravate the wear and erosion caused by the flow of oiland sand. Downstream channel liner 180 is preferably formed of a ceramicmaterial as described above.

[0044] In connection with this embodiment of the invention, a pressurereducing valve has been described which has only upstream and downstreamceramic liners. These ceramic liners are slidably disposed in the fluidflow channels of the pressure reducing valve assembly to protect themetallic walls of the channels from erosive wear. Furthermore, thepressure reducing valve of this embodiment has fewer components than thefirst-described embodiment and thus, is easier to assemble anddisassemble. The upstream liner interconnects with the downstream liner,so as to keep them both securely in place.

[0045] Referring now to FIGS. 14-16, a third embodiment of the pressurereducing assembly is shown and designated generally as 220. The pressurereducing assembly 220 has a valve body 222 and an adjustable valveassembly 240 operable to change the pressure of oil flowing in the line.The valve assembly 240 may be adjusted to vary the pressure in the oilline during operation, and without shutting off equipment or opening thevalve body. The pressure reducing assembly 220 has an upstream channel224 and a downstream channel 226. A flow direction changing cavity 228connects the upstream channel 224 with the downstream channel 226. Theflow direction changing cavity 228 may have a variety of shapes, such acylindrical shape. As in the previous embodiments, the pressure reducingassembly 220 has internal liners and components formed of a ceramicmaterial to provide resistance to wear from sand and other debris inoil.

[0046] As shown in FIG. 14, the body 222 may be formed of any durablematerial such as steel. The upstream channel 224 is fluidly connected tothe direction changing cavity 228 by a circular orifice 234. Oil entersthe body 222 through the upstream channel 224, passes through theorifice 234, and enters the direction changing cavity 228 before exitingthrough the downstream channel 226. An upstream channel liner 225 formedof ceramic material is situated in the upstream channel 224. Similarly,a downstream channel liner 227 formed of ceramic material is positionedin the downstream channel 226. The upstream and downstream channelliners 225, 227 provide barriers that prevent erosion of the inner wallsof the upstream and downstream channels 224, 226 by the oil/sand mixtureflowing from the oil well. In addition, the upstream and downstreamchannel liners 225, 227 are configured to form a tight fit in theupstream and downstream channels 224, 226 respectively. In this way, theliners 225, 227 prevent backwashing of oil and sand between the linersand the channel walls.

[0047] The upstream channel 224 is generally cylindrical and has aninlet portion characterized by a first diameter and an outlet portionthat is characterized by a second diameter smaller than the firstdiameter. The inlet portion and the outlet portion meet at an upstreamchannel maintenance point 229 which serves as a stop for the upstreamchannel liner 225. The upstream channel liner 225 is generallycylindrical and has an inlet portion and an outlet portion. The inletportion of upstream liner 225 has an outside diameter that is generallycommensurate with the diameter of the inlet portion of upstream channel224, and the outlet portion of the upstream liner has an outsidediameter that is generally commensurate with the diameter of the outletportion of the upstream channel. That arrangement provides a shoulderstop 231 on the exterior of the upstream channel liner 225 which abutsthe upstream channel maintenance point 229 when upstream channel lineris inserted into the upstream channel 224. The abutment of the shoulderstop 231 with the maintenance point 229 prevents the upstream channelliner from shifting toward the direction changing cavity 228 when oil isflowing. As in the previous embodiments, the upstream channel liner 225preferably has a flared opening to lessen flow turbulence as the oilenters the upstream channel liner. In addition, the upstream channelliner 225 may have a tapered bore to relieve some of the pressure andturbulent flow of the oil as it flows through the liner.

[0048] The downstream channel 226 is generally cylindrical and has aninlet portion characterized by a first diameter and an outlet portionthat is characterized by a second diameter smaller than the firstdiameter. The inlet portion and the outlet portion meet at an annularshoulder or transition 232 which serves as a stop for the downstreamchannel liner 227. The downstream channel liner 227 is generallycylindrical and has an inlet portion and an outlet portion. The inletportion of downstream liner 227 has an outside diameter that isgenerally commensurate with the diameter of the inlet portion of thedownstream channel 226, and the outlet portion of the downstream linerhas an outside diameter that is generally commensurate with the diameterof the outlet portion of the downstream channel. That arrangementprovides a shoulder stop 233 on the exterior of the downstream channelliner 227 which abuts the transition 232 when the downstream channelliner is inserted into the downstream channel 226. The abutment of theshoulder stop 233 with the transition 232 prevents the downstreamchannel liner 227 from shifting toward downstream components when oil isflowing.

[0049] The valve assembly 240 is configured to form a flow constrictionat the orifice 234 between the upstream channel 224 and the directionchanging cavity 228. In this regard, the valve assembly functions tolimit oil flow and reduce pressure in the oil line. The valve assemblymay have a variety of component configurations to perform this function.A preferred configuration will be described with reference to FIGS. 15and 16. The valve assembly 240 has a disk 242 positioned in thedirection changing cavity 228. The valve disk 242 has a generallycylindrical base 244 and a narrow cylindrical stem 246 that is joinedcoaxially to the base. During operation of the pressure reducingassembly 220, the valve disk 242 is positioned in direct contact withoil that flows through the direction changing cavity 228. Therefore, thevalve disk 242 is formed of a ceramic material that is resistant to wearand abrasion caused by sand and other debris present in oil.

[0050] The valve disk 242 is rotatable in the direction changing cavity228 and is formed to provide control of the pressure in the oil line byadjusting the volumetric flow of the oil from the upstream channel 224into the direction changing cavity 228. To that end, the base 244 ofvalve disk 242 has a sidewall 245. When the valve disk 242 is positionedin the direction changing cavity 228, the sidewall 245 obstructs theorifice 234 between the upstream channel 224 and direction changingcavity 228, as shown in FIG. 14. Referring now to FIG. 16, the base 244has a bottom end 248 that comprises a helical surface 247 and anadjacent planar surface 249. The helical surface 247 begins at theplanar surface section 249 on the bottom end 248 and terminates at apreselected distance from the plane of the planar surface 249. In thepreferred embodiment, the helical surface 247 extends through an angleof approximately 270 degrees about the longitudinal axis of the valvedisk 242.

[0051] Because of the helical surface 247 formed in the bottom end 248,the height of the sidewall 245 varies around the circumference of thebase 244. Thus, the height of the sidewall 245 is a maximum at anangular position where the planar surface 249 is located on bottom end248. The height of the sidewall 245 is a minimum at the angular positionwhere the distance between the helical surface 247 and plane of theplanar surface 249 on the bottom end 248 is a maximum. When the valvedisk 242 is in an angular position in which the planar section 249aligns with the position of the orifice 234, the sidewall 245substantially obstructs the orifice 234. In this position, the “closedposition”, the valve disk 242 substantially blocks flow through theorifice 234. When the disk is in an angular position in which theminimum height portion of the sidewall 245 aligns with the orifice 234,the “full open position”, a passage is established that permits amaximum oil flow through the orifice 243.

[0052] Because the height of sidewall 245 varies around thecircumference of the base 244, the volumetric flow of the oil throughthe orifice 243 can be varied by rotating the valve disk 242 about itslongitudinal axis in the direction changing cavity. In this manner, thevolumetric flow, and thus the fluid pressure, can be adjusted to adesired level.

[0053] Referring now to FIG. 16, the valve disk 242 is connected to acylindrical coupling 250 that is attached over the stem 246. Thecoupling 250 has an outside diameter that is generally commensurate withthe outside diameter of the base 244 on the valve disk 242. Unlike thevalve disk 242, the coupling is not ordinarily exposed to oil that flowsthrough the assembly and need not be formed of a ceramic material.Preferably, the coupling is formed of a durable corrosion resistantmaterial such as stainless steel. The coupling 250 may be attached tothe valve disk 242 in a variety of ways. In the preferred embodiment,the coupling 250 is connected to the stem 246 by a sweat and shrink fitprocess. The coupling 250 has a bore 254 with a diameter generallycommensurate with the outside diameter of the cylindrical stem 246 onthe valve disk 242. Prior to connecting the coupling 250 to the stem246, the coupling is heated so that the diameter of the bore 254expands. The coupling 250 is then lowered over the stem 246 so that thestem extends into the bore 254 of the coupling. The coupling 250 is thenallowed to cool. As the coupling 250 cools, the bore 254 contractsaround the stem 246 to secure the coupling to the valve disk 242.

[0054] The base portion 244 of the valve disk 242 has a top face with ahole 241 that extends into the body of the base, as shown in FIG. 15. Asimilar size hole 251 is formed in the coupling, as shown in FIG. 16.The holes 241, 251 are aligned with one another when the coupling 250 isplaced over the stem portion 246 of the valve disk 242 during the sweatand shrink fit process. Prior to placing the coupling 250 over the stem246, a pin 252 is inserted into hole 241 on base portion 244. The pin252 is configured to project outwardly from hole 241. The portion of thepin 252 that projects from hole 241 is configured to extend into hole251 in coupling 250 when the coupling is lowered over the valve stem 246during the sweat and shrink fit process. Once the coupling 250 and valvedisk 242 are joined, the pin 252 substantially prevents the valve diskfrom rotating relative to the coupling. As such, the valve disk 242 andcoupling 250 are rotatable as a unit.

[0055] A cylindrical liner 260 formed of a ceramic material protects theinner walls of the flow direction changing cavity 228 from abrasioncaused by sand and debris in the oil. The cylindrical liner 260 has abore 266 with a diameter generally commensurate with the outsidediameter of the coupling 250 and the diameter of the base portion 244 ofthe valve disk 242. As such, the liner 260 is adapted to fit over thecoupling 250 and valve disk 242 in the direction changing cavity 228.The liner 260 has a bottom edge with an notch 262 formed therein. Thenotch 262 is aligned with the orifice 234 when the liner 260 is insertedin the direction changing cavity. Once aligned with the orifice 234, thenotch 262 permits fluid communication from the orifice 234 into thedirection changing cavity 228.

[0056] If the assembly 220 requires servicing or removal from the oilline, the oil well is shut down and external isolation valves are closedaround the valve body 222. Oil is drained from the assembly 220. To openthe assembly 220 or remove the assembly from the oil line, the pressurein the assembly must be equalized with ambient pressure outside of theassembly. Referring now to FIG. 14, the valve body 222 preferablyincludes a side port 238 formed by a pair of coaxial bores that alignwith one another and extend through the valve body and liner 260,respectively. The side port 238 is adapted to receive a bleed screw orplug that is inserted into the valve body through the side port 238 ofthe assembly 220. The bleed screw or plug is removable from the sideport 238 to relieve internal pressure in the assembly 220 and facilitateopening of the valve body or removal of the assembly 220 from the line.

[0057] As described above, the downstream channel liner 227 issubstantially prevented from shifting toward downstream components bythe abutment between the shoulder stop 233 and the transition 232. Theshoulder stop 233 and transition 232 maintain the downstream liner 227in an axially fixed position in the downstream channel 226. Thedownstream liner 227 has a top end that functions as a seat 235 for thevalve disk 242. The seat 235 abuts the bottom end 248 of the valve disk242 to limit downstream displacement of the valve disk. The top end ofthe downstream liner 227 also forms a circumferential groove 236. Thegroove 236 is adapted to receive and abut the bottom edge of the liner260. As such, downstream liner 227 substantially prevents downstreamdisplacement of the valve disk 242 and liner 260 in the directionchanging cavity 228.

[0058] A removable bonnet collar or end cap 280 is provided to allowaccess to the interior of the valve assembly 220. The end cap 280 isconfigured to close and seal the direction changing cavity 228 so as toprevent the release of oil flowing from the assembly 220. The cap 280may be secured to the valve body 222 using fasteners, threads, clamps,or other connecting means. In the embodiment shown in FIG. 15, the cap280 has a plurality of holes 282 that can be aligned with correspondingthreaded holes 284 extending into the valve body 222. When the cap 280is placed over the valve body 222 and the holes 282, 284 are aligned,the cap is secured to the valve body by a plurality of bolts 286 thatare inserted into the holes 282, 284. The bolts 286 have threads thatmate with the threads in the hole 284.

[0059] Referring now to FIG. 14, a retainer 270 is provided in the endcap 280 and extends partially into the direction changing cavity 228.The end cap 280 has a cavity that conforms to the exterior shape of theretainer 270. As such, the end cap 280 tightly engages with the retainerwhen the end cap is secured to the valve body 222, thereby securing theretainer in place. The coupling 250 and cavity liner 260 each have topedges that abut the retainer 270. More specifically, the retainer 270has a narrow rim 272 that extends into the direction changing cavity 228to engage the coupling 250 and cavity liner 260. When the end cap 280 ispositioned over the retainer 270 and secured to valve body 222, theretainer substantially prevents axial displacement of the coupling 250and liner 260 toward the end cap during periods when the coupling andliner are subject to high operating pressures. The rim 272 also forms afirst fluid tight seal that prevents oil from seeping out of thedirection changing cavity 228.

[0060] The retainer 270 also has a circumferential flange 274 that abutsthe top of the valve body 222. The flange 274 forms a second fluid tightseal that prevents oil from seeping out of the valve body 222. A bore276 extends through the retainer 270 in coaxial alignment with thelongitudinal axis of the retainer and direction changing cavity 228, ashown in FIG. 15.

[0061] A shaft 290 having an upper end 292 and a lower end 294 isconnected to the coupling 250. The shaft 290 connects the valve assembly240 to an external mechanism that is operable to rotate the collar 200and valve disk 242. The shaft 290 extends through the retainer 270 andvalve body 222 and projects into the valve assembly 240. The lower end294 of shaft 290 has a diameter generally commensurate with the diameterof the bore 254 in coupling 250. The lower end 294 is inserted into thebore 254 to connect the shaft to the coupling 250. The coupling 250 andlower end 294 of the shaft 290 are both metallic and may be connected bya weld or other mechanical connection of comparable strength. Onceconnected to the coupling 250, torque may be applied to the shaft 290 torotate the coupling and valve disk 242. The bores 266, 276 of the cavityliner 260 and retainer 270 are dimensioned to provide adequate clearanceso that the shaft can rotate freely without bearing or rubbing againstsurfaces inside the cavity liner 260 and retainer 270.

[0062] The upper end 292 of shaft 290 extends outside the cap 280 and isadapted for attachment to a lever bar, wheel handle, or other externalmechanism (not shown) that can apply torque to the shaft. The upper endmay have a variety of configurations to connect with the externalmechanism. In FIG. 15, the upper end 292 has a square-shaped transversecross-section that may be inserted into the hub of a wheel handle orcoupled to the drive shaft of drive mechanism. The pressure reducingassembly 220 may be used with a variety of operative devices, includingbut not limited to lever or wheel handles for manual operation, orpneumatic or motor driven actuators with or without gear reduction.

[0063] Preferably, the pressure reducing assembly 220 has a stopmechanism that prevents the valve disk 242 from being rotated from theclosed position directly into the full open position, and vice versa. Inthis way, the range of rotation of the valve disk 242 is limited so thatthe assembly 220 is not subject to a rapid pressure change resultingfrom rotation of the disk from the closed position directly to or fromthe full open position. The stop mechanism may be incorporated into theexternal operation mechanism.

[0064] The valve disk 242 is formed of any technical ceramic material,including aluminum oxide (alumina), chromium oxide, high alumina,titanium oxide (titania), zirconium oxide (zirconia) ceramics, includingfully and partially stabilized zirconia, and combinations of such metaloxides. By using a ceramic material, the valve disk 242 can be formed tovery precise dimensions to provide optimum flow characteristics. Theceramic material is also more resistant to abrasion and wear thanmetallic materials. As a result, the ceramic surfaces are less prone toabrasion and channeling, which can adversely affect the flow propertiesof the recess. Valve disks formed of foundry forged steel or other metalalloys would not provide the same performance and are not as desirableas the ceramic material. In particular, prolonged abrasion on metalsurfaces around the recess can lead to gross failure of the valve diskin a relatively short period of time. Therefore, the ceramic componentsof the present invention provide precise pressure control and offer alonger service life than components made of metal alloys.

[0065] The valve assembly 240 provides an advantage over other meteredpressure reducers. In most of such devices, the pressure reducer isthreaded into the downstream channel wall and rotated within the flowchannel to move the reducer up and down. Threads can become galled andclogged by debris, and must be lubricated with grease to minimizebinding. The valve disk 242 in the present embodiment slidably engagesthe side wall of the direction changing cavity 228 and is limited torotational displacement. The axial position of the valve disk 242relative to the direction changing cavity 228 is fixed by the seat 235on the downstream channel liner 227 and the rim 272 on the retainer 270.With this arrangement, the valve disk 242 does not move longitudinallywithin the cavity 228. Frictional resistance between the side wall ofthe direction changing cavity 228 and the valve disk 242 does notsignificantly impede rotation of the disk. Therefore, there is norequirement for lubrication.

[0066] It can be seen from the foregoing description and theaccompanying drawings that the present invention provides a novel meansfor extending the operating life of high pressure oil well componentsand for maintaining desired operating pressures by substantiallyreducing the rate of abrasive wear to components in a pressure reducingassembly for a high pressure oil well head. Although the invention hasbeen described with reference to specific components and assembliesthereof, including a ceramic pressure reducer, a ceramic-lined reducingvalve, ceramic-lined spool pipe adapters, and ceramic disks, it iscontemplated that any metal component in such a pressure reducingassembly that is subject to erosive wear caused by the flow of anoil/sand mixture under very high pressure can be formed from or linedwith a ceramic material to substantially reduce the rate of wear anderosion. A distinct advantage of the present invention is that a highpressure oil well, incorporating ceramic components in accordance withthis invention, can be operated, at the desired high well pressureswhile keeping the sand content low. The desired high pressures can bemaintained over a much longer period of time than obtainable with knowncomponents because component deterioration is minimized. In addition,the use of ceramic material has the unexpected benefit of providingintricate flow channel design that is not affected by abrasive elementsin oil. Lost oil production resulting from well down-time, during spentcomponent replacement, is drastically reduced, because of the increasedwear resistance and more efficient flow design of the ceramiccomponents.

[0067] It will be recognized by those skilled in the art that changes ormodifications may be made to the above described embodiments withoutdeparting from the broad, inventive concepts of the invention. The termsand expressions which have been employed above are used as terms ofdescription and not of limitation. There is no intention in the use ofsuch terms and expressions of excluding any equivalents of the featuresshown and described or portions thereof. For example, the valve assembly240 described in the third embodiment was described as having a disk 242with a helical bottom end surface 247 and a sidewall 245 that varies inheight. The disk 242 forms a flow passage when sections of the sidewallhaving a reduced height are aligned with the upstream channel. Thepresent invention may also be used with an oval-shaped disk or body thatrotates in a cylindrical chamber. The oval-shaped disk engages thechamber wall on a portion of its perimeter, creating gaps that may bealigned with the upstream channel when the oval-shaped disk is rotatedto permit passage of oil through the chamber. Alternatively, the presentinvention may be used with a disk having a uniform height that featuresa conduit extending through the interior of the disk. In thisembodiment, the conduit enters through the sidewall of the disk, passesthrough the interior of the disk and exits through the bottom edge ofthe disk. The conduit forms an opening through the sidewall of the diskthat can be partially or completely aligned with the upstream channel topermit controlled flow of oil through the disk and chamber, said openingalso being rotatable out of alignment with the upstream channel toprevent passage of oil through the chamber. Accordingly, the inventionincorporates many variations that fall within the scope of the followingclaims.

I claim:
 1. A pressure reducing assembly for a high pressure oil well,comprising: A. an upstream channel; B. a hollow housing having a portthat fluidly connects the housing with the upstream channel; C. a diskdisposed in the housing and rotatable between a first orientation inwhich the port is substantially obstructed by the disk and a secondorientation in which the port is substantially unobstructed by the disk;and D. a downstream channel, wherein the disk has a side wall thatcovers the port when the disk is rotated to the first orientation tosubstantially prevent fluid in the upstream channel from entering thehousing.
 2. The pressure reducing assembly of claim 1, wherein the diskis mounted on a shaft that extends outside the housing and is operableto rotate the disk between the first orientation and the secondorientation.
 3. The pressure reducing assembly of claim 1, wherein thedisk is formed of a ceramic material.
 4. The pressure reducing assemblyof claim 3, wherein the disk is formed of a technical ceramic materialselected from the group consisting of alumina, chromium oxide, titania,zirconia, partially stabilized zirconia, silicon nitride, siliconcarbide, and combinations thereof.
 5. The pressure reducing assembly ofclaim 1, wherein the disk comprises a cylindrical body having a radiallyrelieved recess configured to align with the port and permit the flow offluid from the upstream channel into the housing when the disk isrotated from the first orientation to the second orientation.
 6. Apressure reducing assembly for a high pressure oil well, comprising: A.a hollow body having an upstream channel and a downstream channel; B. aflow channel between the upstream channel and the downstream channel,said flow channel having a longitudinal axis; and C. a disk having abottom edge and disposed in the flow channel, said disk being rotatablein a fixed position on the longitudinal axis of the flow channel toalter the pressure of fluid passing through the flow channel, whereinthe disk comprises a recess along the bottom edge of the disk thataligns with the upstream channel, said recess having a transversecross-sectional area smaller that the cross-sectional area of theupstream channel so as to form a flow constriction that reduces thepressure of fluid as it passes through the flow chamber.
 7. The pressurereducing assembly of claim 6, wherein the recess has a cross-sectionalarea that increases gradually to form a generally helical bottom edge,such that rotation of the disk changes the size of the flow constrictionformed by the alignment between the upstream channel and the recess. 8.The pressure reducing assembly of claim 6, wherein the disk is formed ofa ceramic material.
 9. The pressure reducing assembly of claim 8,wherein the disk is formed of a technical ceramic material selected fromthe group consisting of alumina, chromium oxide, titania, zirconia,partially stabilized zirconia, silicon nitride, silicon carbide, andcombinations thereof.
 10. A pressure reducing assembly for a highpressure oil well, comprising: a housing formed of a metallic material,said housing including an upstream channel, a downstream channel, and apressure reducing chamber disposed between said upstream and downstreamchannels; an inlet port for permitting fluid communication between saidupstream channel and said pressure reducing chamber; an outlet port forpermitting fluid communication between said pressure reducing chamberand said downstream channel; a disk disposed in said pressure reducingchamber, said disk having a sidewall that abuts said inlet port and abottom end that abuts said outlet port, said disk being formed such thatthe height of the sidewall varies from a maximum height to a minimumheight around the circumference of said disk; and means for rotatingsaid disk within the pressure reducing chamber such that the height ofthe sidewall facing said inlet port can be varied, whereby oil flowthrough the pressure reducing assembly can be throttled.
 11. Thepressure reducing assembly of claim 10 wherein the bottom end of saiddisk comprises a helical surface.
 12. The pressure reducing assembly ofclaim 11 wherein the bottom end of said disk further comprises a planarsurface disposed at an angular position where the height of the sidewallis a maximum.
 13. The pressure reducing assembly of claim 12 whereinsaid helical surface begins at said planar surface and terminates at apreselected distance from the plane of said planar surface.
 14. Thepressure reducing assembly of claim 10, wherein the disk is formed of aceramic material.
 15. The pressure reducing assembly of claim 14,wherein the disk is formed of a technical ceramic material selected fromthe group consisting of alumina, chromium oxide, titania, zirconia,partially stabilized zirconia, silicon nitride, silicon carbide, andcombinations thereof.
 16. A pressure reducing assembly for a highpressure oil well, comprising: a housing formed of a metallic material,said housing including an upstream channel, a downstream channel, and apressure reducing chamber disposed between said upstream and downstreamchannels; an inlet port between said upstream channel and said pressurereducing chamber for permitting fluid communication between saidupstream channel and said pressure reducing chamber; an outlet portbetween said pressure reducing chamber and said downstream channel forpermitting fluid communication between said pressure reducing chamberand said downstream channel; a disk disposed in said pressure reducingchamber, said disk having a sidewall and a bottom end, said disk havinga passageway formed therein between the sidewall and the bottom end,said passageway having a first aperture in the sidewall and a secondaperture in the bottom end; means for rotating said disk within thepressure reducing chamber such that the first aperture can be moved intoor out of alignment with said inlet port, whereby oil flow through thepressure reducing assembly can be throttled.
 17. The pressure reducingassembly of claim 16 wherein the bottom end of said disk comprises ahelical surface.
 18. The pressure reducing assembly of claim 17 whereinthe bottom-end of said disk further comprises a planar surface disposedat an angular position where the height of the sidewall is a maximum.19. The pressure reducing assembly of claim 18 wherein said helicalsurface begins at said planar surface and terminates at a preselecteddistance from the plane of said planar surface.
 20. The pressurereducing assembly of claim 16, wherein the disk is formed of a ceramicmaterial.
 21. The pressure reducing assembly of claim 20, wherein thedisk is formed of a technical ceramic material selected from the groupconsisting of alumina, chromium oxide, titania, zirconia, partiallystabilized zirconia, silicon nitride, silicon carbide, and combinationsthereof.